UBC Theses and Dissertations
Survival of laboratory fabricated space maintainers Zhao, Ming Hui
Objective: Few studies have examined the longevity of a large sample of space maintainers. The aim of this research was to determine if appliance, patient or provider factors played a role in the success and survival of laboratory-fabricated fixed space maintainers. Methods: A retrospective chart review was conducted of laboratory-fabricated fixed passive space maintainers inserted between January 1, 2000 and December 31, 2003 in a metro Vancouver pediatric dentistry/orthodontic practice. Appliances were followed until removal or, if still in use, to study’s end point; no observations were censored. Patients lost to follow-up were excluded. All appliances had been prepared and inserted using a consistent, meticulous technique. If an appliance failed prematurely, reasons for failure, e.g. cement loss, solder breakage, eruption interference, were recorded. Other data collected included child’s date of birth, gender, cement type, caries rate, oral hygiene score and patient cooperation at the time of appliance placement. Statistical analyses included descriptive statistics, Kaplan-Meier and the Mantel-Cox Log-rank survival analysis. Results: Of the original sample of 1218, 892 appliances were analyzed. The sample included band and loop (B&L), lingual holding arch (LHA) and Nance appliances from 692 subjects. Subjects were analyzed by specialty: pediatric (n=370), orthodontic (n=322). The mean age at insertion was 9(2) years. For sixty-five percent of subjects (n=452), appliances were deemed ‘successful’ i.e., “did what the clinician expected”. After controlling for the effect of other explanatory variables, type of space maintainer (p<0.03), patient gender (p=0.003) and age at insertion (p<0.0001) were all significantly related to success. Mandibular B&Ls had the longest median survival time (time for half of appliances to fail, MST) of 38 months; maxillary B&Ls, the lowest MST of 22 months. The MST of LHA and Nance were 25 months and 26 months, respectively. In the failure group, no statistical significant differences were found in the MST of space maintainers when appliance type was considered. Conclusion: The majority of the space maintainers lasted their anticipated lifetime. Appliance type, patient gender and age at insertion were significantly associated with outcomes.
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